In the paper "Transformations of infinite series" Bryden Cais gives the following transformations of infinite products[![enter image description here][1]][1][![enter image description here][2]][2]

I obtained the following generalizations of these infinite product transformations
$$
\prod_{n=1}^\infty\left(\frac{1-e^{-\pi\alpha\sqrt{n^2+\beta^2}}}{1+e^{-\pi\alpha\sqrt{n^2+\beta^2}}}\right)^{(-1)^n}=\sqrt{\frac{\tanh\frac{\pi\beta}{2}}{\tanh\frac{\pi\alpha\beta}{2}}}\prod_{n=1}^\infty\left(\frac{1-e^{-\pi\sqrt{n^2/\alpha^2+\beta^2}}}{1+e^{-\pi\sqrt{n^2/\alpha^2+\beta^2}}}\right)^{(-1)^n},\tag{1}
$$
$$
\prod_{n=1}^\infty\left(1-\tfrac{2\sqrt{5}}{1+\sqrt{5}+4\cosh{\frac{2\pi\alpha\sqrt{n^2+\beta^2}}{5}}}\right)^{\left(\frac{n}{5}\right)}=\prod_{n=1}^\infty\left(1-\tfrac{2\sqrt{5}}{1+\sqrt{5}+4\cosh{\frac{2\pi\sqrt{n^2/\alpha^2+\beta^2}}{5}}}\right)^{\left(\frac{n}{5}\right)}.\tag{2}
$$
It is clear that $(1)$ and $(2)$ reduce to theorem 4 and proposition 26 respectively, when $\beta=0$.

Note that infinite products in theorem 4 and proposition 26 are modular forms, however the infinite products in $(1)$ and $(2)$ are not.

>Q: What are the most general modular forms that admit generalized transformation formulas like $(1)$ and $(2)$?

In chapter 5 of his paper Cais gives a general methodology to construct modular forms which then can be generalized as above, thus giving an infinite family of formulas like $(1)$ and $(2)$. Then one can take linear combination of arbitrary number of these functions. Will this be the most general function of this kind or there are others?

Any references regarding these infinite products are welcomed. If the question is not clear please ask in the comments and I will clarify it.

  [1]: https://i.sstatic.net/ZFs6a.png
  [2]: https://i.sstatic.net/3LbJv.png